How Does a Portable Digital TV Work?by Quinten Plummer
Portable DTVs receive digital signals from television station towers by adjusting to the station's broadcast frequency. For example, if a station's broadcast frequency is 126mhz, you would have to match your digital TV to that frequency. The device then demodulates, or decodes, the signal and displays the results on your screen.
The Signals Channels
Digital signals require less bandwidth than analog signals. The efficiency of digital broadcast allows stations to do other things with the freed bandwidth. With the extra bandwidth, some channels provide interactive enhancements like Internet polls and maps. The extra space also allows broadcasters the ability to produce sub-channels. Sub-channels can be used to broadcast HD versions of the same channel or cover out of market sporting events.
Portable DTVs use LCD screens, or "liquid crystal displays." Images are produced via an electric current that stimulates the "liquid crystals" that are pressed between to glass panes. Light from a bulb at the back of the screen is filtered through the crystals. As the electricity morphs crystals, different hues and color are refracted and reflected from the light--producing moving pictures on your screen.